For articles such as goods and items of clothing, imitations in which the appearances are similar to that of genuine articles are being manufactured and sold. In such a situation, in order to guarantee performance, trust, or security, and to maintain brand strength of such articles, techniques for determining the authenticity of articles are required.
As techniques for determining the authenticity of articles, for example, methods of printing special ink on articles, or methods of adhering special small pieces having optical reflective characteristics on articles, are known.
In methods of printing with special ink, predetermined characters and patterns are printed using ink that fluoresces under ultraviolet light. When ultraviolet light is irradiated, the characters and the patterns appear at the surface of the articles, and the authenticity of articles is confirmed. Moreover, the following method is also known. Magnetic material particles or particles having magnetic properties are mixed with ink, and articles have the ink applied thereto. Then, a magnetic sensor is used to determine the authenticity of the articles.
Furthermore, as the small pieces having optical reflective characteristics, the one of using optical characteristics of a hologram or a cholesteric liquid crystal are known. In regard to this technique, for example, Japanese Unexamined Patent Application Publication No. 63-51193 or Japanese Unexamined Patent Application Publication No. 4-144796 is known.